The present invention relates to resilient, three dimensional, perforated plastic webs which are breathable, but are resistant to the transmission of aqueous fluids at least in one direction. According to the present invention the perforated plastic webs consist of a liquid impervious polymeric film having capillaries extending from one surface of the layer, and comprising a first end with an aperture in the opposite surface of the layer, and a second end. From 5% to 50% of these capillaries comprise a second aperture in the second end, wherein they are also preferably higher than the capillaries without the second aperture. The present invention also relates to absorbent articles like baby diapers, adult incontinence articles and in particular to sanitary napkins or pantiliners provided with a backsheet comprising said webs, preferably to provide breathability.
The primary consumer needs which underlie development in the absorbent article field, in particular sanitary napkins, catamenials, or pantiliners is the provision of products providing both a high protection and comfort level.
One means for providing consumer comfort benefits in absorbent articles is by the provision of breathable products. Breathability has typically concentrated on the incorporation of so called xe2x80x98breathable backsheetsxe2x80x99 in the absorbent articles. Commonly utilised breathable backsheets are microporous films and apertured formed films having directional fluid transfer as disclosed in for example U.S. Pat. No. 4,591,523. Both these types of breathable backsheets are vapour permeable allowing gaseous exchange with the environment. This thereby allows for the evaporation of a portion of the fluid stored in the core and increases the circulation of air within the absorbent article. The latter is particularly beneficial as it reduces the sticky and soiled feeling experienced by wearers of or associated with articles comprising an apertured formed film or film like topsheet.
The use of apertured film topsheets has long been recognized as providing particular benefits in controlling the liquid flow through this layer into an absorbent structure and reducing the liquid flow out of the absorbent structure towards the skin of a wearer. In this respect apertured film topsheets have provided an exceptional dryness comfort to the wearers of absorbent articles, particularly sanitary napkins. This comfort benefit, however, started to wear off under stress conditions of such articles, such as physical exercising of the wearer (which also caused transpiration from the skin opposite the article to emanate more strongly), heavy loading of the article or extended wearing duration.
A drawback associated with the use of breathable backsheets in absorbent articles is the negative effect on the protection level performance by leakage, known as wet through, onto the users garment. Although, breathable backsheets in principle only allow the transfer of materials in the gaseous state, physical mechanisms such as extrusion, diffusion and capillary action may still occur and result in the transfer of the fluids from the absorbent core through the backsheet and onto the user""s garments. In particular, these mechanisms become more dominant if the product is utilised during physical exertion, or for heavy discharge loads or over extended periods of time. Thus, whilst the incorporation of breathable backsheets in absorbent articles is highly desirable from a comfort standpoint, since the primary role of a backsheet still remains the prevention of liquid leakage, conventional breathable backsheets have not been successfully incorporated into products.
The problem of wet through onto users garments due to the incorporation of such breathable backsheets in absorbent articles has indeed also been recognized in the art. Attempts to solve the problem have mainly resided in the use of multiple layer backsheets such as those illustrated in U.S. Pat. No. 4,341,216. Similarly European patent application no. 710471 discloses a breathable backsheet comprising an outer layer of a gas permeable, hydrophobic, polymeric fibrous fabric and an inner layer comprising an apertured formed film having directional fluid transport. The backsheet construction preferably has no liquid transport/wet through under certain specified test conditions. Also European patent application no. 710472 discloses a breathable backsheet consisting of at least two breathable layers which are unattached to one another over the core area. The backsheet construction preferably has no liquid transport/wet through under certain specified test conditions.
U.S. Pat. No. 4,713,068 discloses a breathable clothlike barrier for use as an outer cover for absorbent articles. The barrier comprises at least 2 layers, a first layer having a specified basis weight, fiber diameter and pore size and a second layer comprising a continuous film of poly (vinyl alcohol) having a specified thickness. The barrier also has a specified water vapour transmission rate and level of impermeability.
However, these proposed solutions have not been able to provide a fully satisfactory solution to the problem of breathable backsheet wet through under stress conditions. But especially under such stress conditions breathability would have most pronounced comfort benefits especially for articles comprising film topsheets. For such articles the experienced or assumed stickiness, stuffiness, or soil residue between film and skin is greatest under stress conditions.
U.S. Pat. No. 5,591,510 as well as WO 97/03818 and WO 97/103795 disclose an apertured film layer having capillaries which are disposed at an angle relative to the plain of the film, which films are referred to as slanted capillary films. This film structure is provided as an improvement for incorporation into clothing and garments which are breathable, yet non transmitting liquids toward the wearer of such garments. Also the use of such slanted capillary films is indicated in the context of absorbent articles but as a topsheet, particularly in FIG. 16 of U.S. Pat. No. 5,591,510 the combination of such slanted capillary films together with an absorbent material is disclosed, however not in the context of disposable absorbent articles according to the present invention.
In European patent applications Nos. 98101867.4 and 98101868.2, respectively entitled xe2x80x9cAbsorbent article with breathable dual layer backsheet comprising one layer with slanted capillary aperturesxe2x80x9d, and xe2x80x9cAbsorbent article with breathable backsheet comprising slanted capillary apertures and an apertured film topsheetxe2x80x9d, disposable absorbent articles are described such as baby diapers, adult incontinence articles and in particular sanitary napkins or panty liners. Typically such articles comprise a liquid pervious topsheet forming the wearer facing surface of the article, an absorbent core and a breathable backsheet forming the garment facing surface of the article. The absorbent core is interposed between the topsheet and the backsheet.
The breathable backsheet is located on the garment facing surface of the absorbent core and comprises at least one backsheet layer. The backsheet comprises a resilient three dimensional web, which consists of a liquid impervious polymeric backsheet film which backsheet film has apertures. The apertures form capillaries which have side walls which extend away from the wearer facing surface of the backsheet film and towards the absorbent core providing the web with three dimensionality. The capillaries have a first opening in the garment facing surface of the backsheet film and a second opening at the end of the capillaries spaced apart from the wearer facing surface of the backsheet film. The capillaries are slanted, i.e., they extend away from the wearer facing surface of the backsheet film at an angle which is less than 90xc2x0 in respect to the plane of the backsheet film, or, in other embodiments, are curved or bent towards the plane of the backsheet film. Further, in alternative or in addition thereto, the capillaries can have a first and a second portion which are different in direction, form, shape, size or combinations thereof.
Also the second opening of at least some of the capillaries may be provided as slits. Slits are considered to be such forms in which the longest extent of an opening is at least 5 times the length of the smallest length of the opening.
Owing to the directional liquid transport capability of the polymeric backsheet film and to the ability to close under pressure derivable from the angled capillaries the breathable backsheets of the above mentioned European patent applications provide a sanitary article with a good leak through protection while maintaining optimum breathability for improved comfort.
However, the performances of resilient, three dimensional polymeric films having apertures that form capillaries, and preferably slanted capillaries as described above, can still be improved in terms of resistance of the three dimensional structure to crush due to collapse of the capillaries, that could be caused by higher compression forces and stresses exerted on the resilient three dimensional film during the use, for example by particularly severe wearing conditions experienced during the use of preferred absorbent articles comprising said resilient, three dimensional polymeric film in a backsheet structure. This increased resistance is even more desirable when the resilient three dimensional polymeric film comprises capillaries, preferably slanted capillaries, which are particularly slender, i.e. being provided with a higher length as compared to the dimension of the respective first opening in the first, base surface of the polymeric backsheet film, in order to facilitate bending, as descried in the European patent applications filed by the applicant at the same time as the present application, and entitled xe2x80x9cResilient, three dimensional polymeric film comprising capillary aperturesxe2x80x9d (EP 99105197.0, PandG Case CM2063F), and xe2x80x9cAbsorbent article with improved backsheet comprising capillary aperturesxe2x80x9d (EP 99106116.9, PandG Case CM2062F). Increased crush resistance in fact provides such a resilient three dimensional polymeric film with a better ability to close under pressure, combined with a reduced risk of collapse of the structure, and therefore with an increased capability of recovering the initial, undeformed state of the capillaries after release of the applied pressure.
It is therefore an object of the present invention to provide an improved resilient three dimensional polymeric film with apertures that form capillaries, which is provided with an increased resistance to crush and to capillary collapse under compression.
Also, the performances of disposable absorbent articles with preferably breathable backsheets comprising at least a resilient three dimensional polymeric film having apertures that form capillaries, and preferably slanted capillaries as described above, can still be improved in terms of resistance of the three dimensional structure to crush due to collapse of the capillaries, that could be caused by higher compression forces and stresses caused by particularly severe wearing conditions experienced during the use of the absorbent articles comprising said backsheets.
An increased resistance to crush and capillary collapse under pressure for the resilient three dimensional polymeric backsheet film is also desirable in backsheets comprising said film and used in disposable absorbent articles in a context different from breathability, for example in order to take advantage of an improved resiliency of these structures in response to compression forces typically exerted in use perpendicularly to the film surface.
It is therefore a further object of the present invention to provide a disposable absorbent article having a backsheet comprising a resilient three dimensional polymeric film with apertures that form capillaries, which is provided with an increased resistance to crush and to capillary collapse under compression.
It is still a further object of a present invention to provide a preferably breathable disposable absorbent article having improved comfort while maintaining an even better leakage protection, i.e. being exceptionally wet through resistant under the stress and pressure experienced during the use.
The present invention relates to resilient, three dimensional, perforated plastic webs which consist of a liquid impervious polymeric film having a first surface, a second surface, and capillaries. The capillaries have side walls which extend away from the second surface of the film providing the web with three dimensionality. The capillaries have a first end comprising a first opening in the first surface of the film, and a second end spaced apart from the second surface of the film, each of the capillaries defining a conduit constituted by the first end, the second end, and the side walls.
At least 50% of said capillaries are closed capillaries which are closed at the second end, and at least 5% of the capillaries are open capillaries which comprise a second opening at the second end. The open capillaries also preferably extend away from the second surface of the film further than the closed capillaries.
The present invention also relates to disposable absorbent articles of a layered construction such as baby diapers, adult incontinence articles and in particular sanitary napkins or panty liners, which are preferably also breathable. Also articles such as underarm sweat pads or scholar shirts may benefit from the present invention. Typically such articles are of layered construction with each layer or group of layers having a garment facing surface which is oriented to face in the direction of a garment during use of the article and a wearer facing surface facing in the opposite direction. Typically such articles comprise a liquid pervious topsheet forming the wearer facing surface of the article, an absorbent core and a preferably breathable backsheet forming the garment facing surface of the article. The absorbent core is interposed between the topsheet and the backsheet.
The preferably breathable backsheet is located on the garment facing surface of the absorbent core and comprises at least one backsheet layer. The backsheet comprises a resilient, three dimensional web, consisting of a liquid impervious polymeric backsheet film as described above having a garment facing surface, a wearer facing surface, and capillaries. The capillaries have side walls which extend away from the wearer facing surface of the backsheet film towards the absorbent core, providing the web with three dimensionality.